Case 20- Anatomy Flashcards
Blood flow in the brain- Myogenic autoregulation
When the pressure increases vasoconstriction occurs reducing cerebral blood flow. When the pressure decreases there is vasodilation. Autoregulation allows the maintenance of blood flow to the entire brain. Locally in specific regions of the brain CO2 and hydrogen ions cause vasodilationt
Outside the CPP autoregularity limit
- Cerebral blood flow becomes dependent on the mean arterial pressure in a linear fashion
- When the vessels are maximally dilated, they cannot compensate anymore and flow decreases as pressure decreases
- When the vessels are maximally constricted, they cannot compensate anyome and flow increases as pressure increases
Directions in the brain
When describing the brain, Rostral is forward towards the mouth and caudal is towards the back. Dorsal is up near the hair and ventral is down near the neck
Anatomy of the brainstem
Midbrain -> pons -> medulla oblongata
• Hindbrain- pons, medulla and cerebellum
• Bulb- pons and medulla
• Function= conduit and connections between the cerebrum and spinal cord
• Reticular formation- consciousness, respiration and CVS
• Cranial nerves III-XII nuclei
The Cerebral peduncle
The Cerebral peduncle connects the midbrain to the thalamus, it contains the: Crus cerebri (anterior), substantia nigra and the Tegmentum. The crus cerebri consists of axons of the Corticospinal, Corticobulbar and Corticopontine tracts. The space between the two cerebral peduncles is the interpeduncle fossa. The cerebellar peduncles are on the ventral surface
Midbrain dorsal surface
- Superior colliculus- eye movement and reflexes
* Inferior colliculus- auditory reflexes
Midbrain lateral view
- Tegmentum- contains the cranial nerve nuclei
- Tectum- superior and inferior colliculi
- Tegmentum is separated from the Tectum by the cerebral aqueduct which joins the third and fourth ventricle
Rostral level of the midbrain
- Superior colliculus (SC)
- Spinal lemniscus/medial lemniscus (SL/ML)
- Red nucleus (RN)
- Substantia nigra (SN)
- Crus cerebri (CC)- contains the descending motor nerves
Brainstem causal, level of inferior colliculus
- Inferior colliculus (IC)
- Decussation of superior cerebellar peduncle (DCP)
- Spinal lemniscus/medial lemniscus (SL/ML)
- Corticobulbar/corticospinal tracts (CB/CS)
Pons ventral surface
- Middle cerebellar peduncle- area of attachment between the pons and cerebelum
- Pontine swelling due to the transverse fibres between the pons and cerebellum
Pons dorsal surface
- Superior cerebellar peduncle
- Middle cerebellar peduncle
- The cerebellar peduncles form connection with the cerebellum
- Rhomboid fossa- forms the floor of the 4th ventricle
- Lateral aperture- allows the CSF to enter the subarachnoid space from the 4th ventricle
Mid-pons
- Trigeminal nerve (CN V)
- Corticospinal fibres (CS)
- Medial lemniscus (ML)
- Middle cerebellar peduncle (MCP)
- 4th ventricle- opens from the cerebral aqueduct
Medulla ventral surface
- Olives- contains the inferior olivary nucleus, forms connections with the cerebellum
- Pyramids- white matter containing the corticospinal tracts. Contain descending fibres from the motor cortex which pass through the internal capsule and are going to the spinal cord
Medulla- dorsal surface
- Inferior cerebellar peduncle
- Cuneate and gracile tubercle- formed by the dorsal column and carry information about fine touch and proprioception. The cuneate tubercle carry’s information from the upper limb and neck and the gracile tubercle carry’s information from the lower limbs and trunk
- Obex- CSF can enter the central canal of the spinal cord through this
- Fourth ventricle (floor)
Cranial nerves
There are 12 pairs of cranial nerves. They form part of the peripheral nervous system, the cranial nerves arise directly from the brain and brainstem.
The types of cranial nerves
- CN I Olfactory- Sensory
- CN II- Optic- Sensory
- CN III- Oculomotor- Motor
- CN IV- Trochlear- Motor
- CN V- Trigeminal- Both
- CN VI- Abducens- Motor
- CN VII- Facial- Both
- CN VIII- Vestibulocochlear- Sensory
- CN IX- Glossopharyngeal- Both
- CN X- Vagus- Both
- CN XI- Accessory (spinal)- Motor
- CN XII- Hypoglossal- Motor
Cranial nerve mnemonic
Cranial nerve mnemonic= Ooh, ooh, ooh, to touch and feel very good velvet. Such heaven!
Fibre type mnemomic- Some say my mother bought my brother some bad beer, my, my
Sensory function of cranial nerves
- GSA-General somatic afferent-General sensory function- pain, touch and temperature. Of the skin, bone and meninges includes oral cavity, nasal cavity and eye socket
- SSA-Special somatic afferent- sensation developing in the ectoderm e.g. sight, hearing, equilibrium or Special Visceral Afferent- special senses in conjunction with GIT e.g. taste, smell. These are special senses
Motor function of the cranial nerves
- General Somatic Efferent-to skeletal muscles. Muscles of eye and tongue movement (as well as shoulder)
- Special Visceral Efferent-Special motor to skeletal muscles that develop in the pharyngeal branchial arches-give rise to structures in the head and neck. The Branchial muscle such as muscles of mastication, swallowing, speech and facial expression
Autonomic function of the cranial nerves
- General Visceral Efferent- Motor to heart, smooth muscle and glands. These are part of the parasympathetic functions. Salivary glands, lacrimal glands, light reflexes, carotid body, thorax/abdo
- General Visceral Afferent- sensory from organs-smooth muscle, baroreceptor, chemoreceptors, glands e.g. heart and GIT.
Origin of cranial neves
• Cerebrum- cranial nerves 1 and 2 (olfactory and optic)
• Midbrain- cranial nerves 3 and 4
• Pons- cranial nerves 5 to 8
• Medulla- cranial nerves 9 to 12
In general the cranial nerves emerge from the ventral aspect, CNIV trochlear is an exception. In general the cranial nerves emerge sequentially from CN1-12, CN12 hypoglossal is the exception to this rule and is before CN XI. The motor nerve nucleus is more near the midline
Sensory nerve nuclei
- General rules- lateral, better to group by type
- General sensory- spinal trigeminal nucleus controls general sensation (pain, pressure, temperature). Along the length of the brainstem
- Special sensory- vestibulocochlear nuclei (hearing and balance), nucleus solitarius (taste)
Parasympathetic function of cranial nerves
- The parasympathetic innervation to the entire body comes from 4 cranial nerves and the sacral plexus
- CN3 Oculomotor- Pupil reflex
- CN7 Facial- Lacrimal, sublingual and submandibular glands
- CN9 Glossopharyngeal- Parotid salivary gland
- CN10 Vagus- Thorax and abdomen as far as midgut
Parasympathetic nerve nuclei
- Midline, 4 cranial nerves. In numerical order from superior to inferior
- Edinger- Westphal nucleus (CN3)- Occulomotor, Pupillary reflex
- Superior salivatory nucleus (CN7)- Facial, saliva and tears
- Inferior salivatory nucleus (CN9)- Glossopharyngeal, saliva
- Dorsal vagal nucleus (CN10)- Vagus, thorax and abdomen
CN I- Olfactory
- Course- enters the cranial cavity via the cribiform plate of the ethmoid bone, goes through the Olfactors bulb and terminates in the limbic system
- Function= special sense (SSA)- smell
- Clinical testing- has the patient noticed any changes to their sense of smell
CNII-Optic, III-Oculomotor, IV-Trochlear, VI-Abducens
- II- enters the orbit via the optic canal. Special sense (SSA)- vision
- III, IV, VI- enter the orbit via the superior orbital fissure
- III= Motor (GSE)- extraocular muscles. Parasympathetic (GVE)- light reflex/accommodation
- IV= Motor (GSE)- extraocular muscles
- VI= Motor (GSE)- extraocular muscles
- Clinical testing: separate eye and CN II, III, IV and VI examination
CNV Trigeminal nerve
- Trigeminal sensory function overview= anterior 2/3rds of the head, dura matter and cranial blood vessels
- V1- Ophthalmic- goes through the superior orbital fissure. Sensory function in the forehead, cornea, upper eyelid and dorsal nose
- V2- Maxillary- goes through the foramen rotundum. Sensory function in the lateral nose, upper teeth, hard palate, upper cheek
- V3- Mandibular- goes through the foramen ovale. Sensory function in the lower jaw, lower teeth, chin, posterior cheek, temple and anterior 2/3rds of the tongue
Motor function of the mandibular branch V3
Muscles of mastication:
1) Temporalis- elevation and retraction
2) Masseter- elevation
3) Lateral Pterygoid- protrusion and side to aide movement
4) Medial Pterygoid)- elevation and side to side movement
Mylohyoid, Anterior belly of digastric, Tensor palatini and Tensor tympani.
Branches of CNVII (facial)
• Temporal • Zygomatic • Buccal • Marginal mandibular • Cervical Goes through the Internal acoustic meatus in the petrous part of the temporal bone and exits through the Stylomastoid foramen
CNVII (facial)
- Function- motor (SVE): Muscles of facial expression, Stylohyoid, Posterior belly of digastric, Stapedius
- Sensory function= General (GSA)- external ear, Special sense (SSA)- taste in the anterior 2/3 of the tongue. To test you ask if there is any change in taste
- Parasympathetic function (GVE)= Lacrimal gland (greater petrosal nerve), Nasopalatine gland, Submandibular and Sublingual glands (chorda tympani to lingual)
- Clinical testing= muscles of facial expression, ask if there is any change in hearing
- Chorda tympani= a branch of the CNVII, it joins the lingual nerve (CNV3) to provide taste to the anterior 2/3rds of the tongue. It arises from the facial nerve as it goes through the inner ear
Facial nerve rhyme
- Closes your eye - facial expression
- Tastes pie - Anterior 2/3 tongue
- Makes your cry - Innervation of lacrimal gland (plus submandibular and sublingual salivary glands).
CNVIII- Vestibulocochlear
- Course- through the internal acoustic meatus
- Function- special senses (SSA), hearing and balance
- Clinical testing- separate ear and CNVIII examination
CNIX- Glossopharyngeal
- Exits the skull via the jugular foramen, passes down the neck and divides into branches
- Sensory= General (GSA)- Posterior 1/3 tongue and oropharynx. Special sense (SSA)- taste in the posterior 1/3 of the tongue
- Motor (SVE)- Stylopharyngeus
- Autonomic function= Parasympathetic (GVE)- Parotid gland (lesser petrosal nerve). Sensory from viscera (GVA)- carotid body and sinus
- The carotid body measures oxygen the carotid sinus measures blood pressure.
- The carotid sinus is a dilation of the lower end of the internal carotid and acts as a baroreceptor. The carotid body is posterior to carotid bifurcation or between its branches. It detects hypoxia, hypercapnia and increased H ion concentration
CNX- Vagus
• Exits the skull via the jugular foramen, passes down the neck in the carotid sheath with the internal jugular vein and internal carotid (CCA). Gives branches
The uvula deviates away from the side with the lesion. A weak bovine cough is due to a vagus nerve lesion
• Sensory function= General (GSA)- laryngopharynx, larynx, outer ear. Special sense (SSA)- taste in the epiglottis and pharynx
• Motor (SVE)= Larynx, Pharynx (all except stylopharyngeus). Soft palate- all except tensor veli palatini. Tongue- only palatoglossus
• Autonomic= Parasympathetic (GVE) and sensory (GVA)- thorax and abdomen control up to the splenic flexure
Clinical testing of CN IX and X
Assess the patients; swallow, speech, cough, uvula, nasal air leak. Ask if there is any problems and mention gag reflex
CNXI- Accessory
- Course- exits the skull via the jugular foramen. Passes through the sternocleidomastoid into the posterior triangle and on to the trapezius
- Motor function (GSE)- Trapezius, SCM
- Clinical testing= turning your head against resistance (SCM), shrug your shoulders (trapezius)
CNXII- Hypoglossal
• Can be seen in the neck just inferior to the posterior belly of the digastric (a suprahyoid muscle)
• Motor function (GSE) extrinsic muscles which move the tongue- Genioglossus, Hyoglossus, Styloglossus
• Motor function (GSE) intrinsic muscles- change the shape of the tongue i.e. phonation, eating and swallowing
• Clinical testing= observe the tongue. Stick out their tongue, move side to side, push into their cheeks against resistance. Speech
The tongue deviates towards the side there has been a lesion in
Tongue innervation
- Motor- Palatoglossus CNX, all other extrinsic and intrinsic muscles CNXII
- Sensory in the posterior 1/3rd= CN9 taste and general sensation
- Sensory in the anterior 2/3rd= CN7 taste, CNV3 (Lingual)- general sensation
The internal and external carotid artery
The Internal Carotid artery (ICA) enters the cranium and supplies the brain, forehead and scalp. The External Carotid artery (ECA) supplies the neck, face and scalp.
The branches of the external carotid
- SOME- superior thyroid
- ANATOMISTS- Ascending Pharyngeal
- LIKE- Lingual
- FREAKING- Facial
- OUT- Occipital
- POOR- Posterior Auricular
- MEDICAL- Maxillary
- STUDENTS- Superficial temporal
The anterior, posterior and terminal branches of the ECA
1) The ascending branches of the ECA include the Superior thyroid, Lingual and Facial arter
2) The posterior branches of the ECA are the Ascending Pharyngeal, Occipital and the Posterior Auricular
3) The terminal branches of the ECA are the Maxillary and Superficial temporal artery
Overview of the facial artery and its branches
The facial artery passes through the submandibular salivary gland and passes posterior to the mandible and masseter. It ascends along the face in a superomedial direction. Branches:
• Angular- around the orbit
• Lateral nasal- external portion of the nosse
• Superior labial- mouth
• Inferior labial- mouth
The Occipital and Posterior Auricular artery
- The Occipital artery passes deep to the posterior belly of the digastric, it supplies the posterior aspect of the scalp.
- The posterior auricular artery passes between the external auditory meatus and the mastoid process. It supplies the scalp posterior to the ear.
The Maxillary and Superficial temporal artery
- Superficial temporal artery- ascends on the squamous portion of the temporal bone, contributes to the supply of the face and scalp. Has three branches; the Transverse facial, Frontal branch and the Parietal branch. The transverse facial branch travels through the parotid gland to supply the face. The frontal and parietal branch supply the lateral branch
- Maxillary artery- the maxillary artery runs deep to the mandible. It courses medially towards the nasal cavity. Has three branches: infra-orbital, Buccal artery and the Mental artery. The infra-orbital branch supplies from nose to upper lip. The Buccal artery is superficial to the Buccinator. The mental artery supplies the chin
The branches of the Opthalmic artery
The ophthalmic artery is a branch of the ICA, it enters through the Optic canal. The branches:
• Dorsal nasal artery- face
• Supratrochlear artery- forehead and scalp
• Supra-orbital artery- forehead and scalp
• Lacrimal artery- branch into Zygomaticotemporal and Zygomaticofacial which go on to supply the face
The ECA supply to the face
- Facial
- Superficial temporal (transverse facial)
- Maxillary
The ECA supply to the scalp
- Superficial temporal
- Occipital
- Posterior auricular
Venous drainage of the face
- Via the facial vein (and its tributaries the Supraorbital and Supratrochlear)
- Supraorbital and supratrochlear veins form the angular vein
- Angular vein -> facial vein -> IJV
Venous drainage of the scalp
- Anterior: Supraorbital and supratrochlear veins
- Lateral: Superficial temporal vein
- Posterior: Posterior auricular and occipital veins
Retromandibular vein
- The Superficial temporal and maxillary veins join to form the retromandibular vein
- The retromandibular vein has anterior and posterior branches
- It travels through the parotid gland
- The anterior branch combines with the facial vein to form the IJV, the IJV with the subclavian form the brachiocephalic vein
- The posterior branch combines with the posterior auricular vein to form the EJV. The EJV empties into the subclavian vein.
The Facial vein
The facial vein has connections with the Ophthalmic veins, infraorbital, the deep facial vein and the pterygoid plexus. These veins have connections with the cavernous sinus. There is risk of infections from the triangle of danger spreading intracranially.
Cranial nerves with motor function
CN III- Occulomotor CN IV- Trochlear CN V- Trigeminal CN VI- Abducens CN VII- Facial CN IX/X- Nucleus ambiguus CN XI- Accessory CN XII- Hypoglossal Arranged in numerical order
Testing the trigeminal nerve
1) Sensation over the face
2) Corneal reflex
3) Jaw jerk reflex
4) Function of the muscles of mastication
